Sodium azide serves as the gas-generating charge in virtually all of the gas generating air-bag systems currently utilized in automotive air-bag systems. Two methods of manufacturing sodium azide are known in the art. The first is the so-called sodamide process which comprises the reaction of liquid sodium with liquid ammonia, followed by the addition of nitrous oxide to give sodium azide and sodium hydroxide. Unfortunately, this process has been plagued by several fires in commercial operation in recent years.
The second known process is the so-called hydrazine-nitrite process. This process comprises the reaction of hydrazine with an alkyl nitrite in the presence of a base such as sodium hydroxide. Typically, the alkyl nitrite is produced by reacting an alkyl alcohol, sulfuric acid and sodium nitrite, and the desired product phase separates and is collected and purified. Unfortunately, the alkyl nitrite of choice is butyl or a higher carbon analogue since the lower alkyl nitrites suffer from a low boiling point (and hence volatility) problem. Moreover, the butyl alcohol and higher carbon alcohol precursors are more expensive than might be desired. In a variation of this process, U.S. Pat. No. 1,628,380 discloses a batch process for making sodium azide utilizing absolute ethyl alcohol; however, this patent notes that "a violent reaction set in and pure white sodium azide is thrown out of solution" (emphasis inserted).
New methods of producing the desired azide salts that are less expensive, and less subject to the fire hazard or other violent reaction described above would be highly desired by the automotive air-bag manufacturing community.